LINQ To TypeScript

• Implementation of LINQ for TypeScript
• Targets TypeScript 3.9.X and ES 2018

await from([bing, google, quackQuackGo])
    .asParallel()
    .selectAsync(downloadHtml)
    .select(getTitle)
    .toArray()

Getting Started

npm i linq-to-typescript

tsconfig.json

"compilerOptions": {
    "target": "es2018",
    "lib": [
      "dom",
      "es2018"
    ],
    "importHelpers": true
}

• The strict TS option is recommended.
• Library is dependent on tslib for async iteration polyfills.

Using the Library

With Wrappers

// 0. Import Module
import { from } from "linq-to-typescript"

// To Use With Wrappers
const evenNumbers = from([1, 2, 3, 4, 5, 6, 7, 8, 9]).where((x) => x % 2 === 0).toArray()

Without Wrappers

// 0. Import Module
import { initializeLinq, IEnumerable } from "linq-to-typescript"
// 1. Declare that the JS types implement the IEnumerable interface
declare global {
    interface Array<T> extends IEnumerable<T> { }
    interface Uint8Array extends IEnumerable<number> { }
    interface Uint8ClampedArray extends IEnumerable<number> { }
    interface Uint16Array extends IEnumerable<number> { }
    interface Uint32Array extends IEnumerable<number> { }
    interface Int8Array extends IEnumerable<number> { }
    interface Int16Array extends IEnumerable<number> { }
    interface Int32Array extends IEnumerable<number> { }
    interface Float32Array extends IEnumerable<number> { }
    interface Float64Array extends IEnumerable<number> { }
    interface Map<K, V> extends IEnumerable<[K, V]> { }
    interface Set<T> extends IEnumerable<T> { }
    interface String extends IEnumerable<string> { }
}
// 2. Bind Linq Functions to Array and Map
initializeLinq()
// 3. Use without a wrapper type
const evenNumbers = [1, 2, 3, 4, 5, 6, 7, 8, 9].where((x) => x % 2 === 0).toArray()

Examples

Please refer to EXAMPLES.md

API

LinqToTypeScript implements the functionality of the IEnumerable interface

• IEnumerable, IAsyncEnumerable, and IParallelEnumerable interfaces are based on,
• IEnumerable<T> Interface
• Some changes made due to conflics with existing method names
• Some changes made due to limitations of JavaScript

IEnumerable

• Inspired by LINQ API Surface
• Has Async methods that return Promise or IAsyncEnumerable
• Implements Iterable<T>
• Use from to wrap your arrays

IAsyncEnumerable

• Inspired by LINQ API Surface
• Has Async methods that return Promise or IAsyncEnumerable
• For asynchronous iteration
• Implements AsyncIterable<T> interface
• Use fromAsync to wrap your AsyncIterable type

IParallelEnumerable

• Inspired by LINQ API Surface
• Has Async methods that return Promise or IParallelEnumerable
• For asynchronous iteration in parallel (where possible)
• Implements AsyncIterable<T> interface
• Use fromParallel to create a parallel enumeration

Shared Instance Methods

* Async methods take an async function

Static Methods

Index Methods

Exception Types

TypeDoc Documentation

Refer to https://arogozine.github.io/linqtotypescript/

Design

Binding new APIs to Array Types

JavaScript doesn't have extension methods like in C#, therefore we extend the class itself with new methods. Call initializeLinq to bind library functions to default Array methods,

The following collections support IEnumerable,

• Array
• Map
• Set
• String
• Int8Array
• Int16Array
• Int32Array
• Uint8Array
• Uint8ClampedArray
• Uint16Array
• Uint32Array
• Float32Array
• Float64Array

Using Wrappers

NOTE: Wrappers are safer as they won't interfere with other libraries.

// To Create an IEnumerable<T>
import { from } from "linq-to-typescript"
from(iterableIteratorOrArray)

// To Create an IAsyncEnumerable<T>
import { fromAsync } from "linq-to-typescript"
fromAsync(asyncIterableIteratorOrPromiseArray)

// To Create an IParallelEnumerable<T>
// You have to specify the parallel generator function type
import { fromParallel, ParallelGeneratorType } from "linq-to-typescript"
fromParallel(ParallelGeneratorType.PromiseToArray, asyncFuncThatReturnsAnArray)

F.A.Q.

Q I am getting a Error: Cannot find module 'tslib' error.

A This library depends on tslib. Run npm i tslib to solve the error.

Q Why did you create this?

A For fun and to gain understanding of TypeScript and Node Package Manager.

Q What's needed to target ES2018?

A This library uses iteration and async iteration. You may need polyfills for Iterator and AsyncIterator. Libraries such as core js have this.

Q Can this run in an ES5 browser like Internet Explorer.

A With the right transpiler, polyfills, and bundler. Its not recommended due to the size and most likely major performance impact.

Q How does this compare to other LINQ libraries?

A Other libraries tend to use eager evaluation and work with arrays instead of iterables.

Q Why should I use this instead of lodash or something similar?

A

• TypeScript first. Libraries which target JavaScript first do additional type checking which can have a negative impact on performance.
• This library uses iterators and generators. Evaluation is lazy, not eager like JS array operations. These are new language features which have no support in legacy browsers like IE11.

Q Which browsers are supported?

A

• Firefox, Chrome, and Edge. IE is not supported.
• A good bundler targeting ES5 should allow IE support (with proper ES6/ES7 polyfils).

Q Can I contribute?

A Please do!